Papers relating to his work as Engineer-in-Chief, South East Asia Command, 1943-1946, dated 1943-1947, principally comprising official photographs showing construction work on roads, bridges and airstrips, 1943-1946; official photograph of Acting Adm Louis (Francis Albert Victor Nicholas) Mountbatten, Supreme Allied Commander South East Asia and US Gen Lewis APick, [1945]; 'The construction of forward airfields in SEAC Areas', Engineer-in-Chief (India) Pamphlet No 12, prepared by Harrison and Maj Gen Horace Eckford Roome, Engineer-in-Chief, General HQ, India, 1945; 'Royal Engineers training memorandum No 20: rafting andbridging', pamphlet issued by the War Office, 1946; 'Memorandum on the training and employment of officers of the Royal Engineers and Indian Engineers in preparation for war', issued by General HQ, Delhi, 1945; letter from Harrison to AQ Plans, South East Asia Command relating to the building of the Ledo Road, Burma and India, Dec 1945; 'Major Engineer: lessons of the war in South East AsiaCommand', copy of unsigned typescript text, [1945]; pre-publication edition of Mountbatten's Report to Combined Chiefs of Staff by the Supreme Allied Commander South East Asia, 1943-1946 (London, 1951), 1947; 'Annexure A', unsigned typescript text on Engineer organisation, South East Asia Command, 1943-1946, written in [1946] and later reworked and published as Annexure 6 of Mountbatten's Report to Combined Chiefs of Staff by Supreme Allied Commander South East Asia, 1943-1946 (London, 1951). Unsigned text of lecture to the Senior Officers' School on organisation and work of Royal Engineers, 31 Dec 1941.

Copy of typescript extract from letter, dated 16 Dec 1940, by Hingston, General Staff Officer 3 (Intelligence), Headquarters, 4 Indian Div, Western Desert, to his wife at General Headquarters, Delhi, India, with detailed uncensored account of British success in Operation COMPASS, 1st Western Desert campaign, 6-16 Dec 1940. Typescript notes by Mrs Hingston on Hingston's health and pre-war service in India [1997].

Unpublished typescript memoirs, 1893-1969, including: accounts of life in the British colony in St Petersburg before World War One; work in the British Military Mission at the Russian War Office; events witnessed during the Russian Revolution and conditions for the Russian Army during the Revolution, 1917-1918; evacuation of British personnel from Russia, February 1918; negotiating with Finnish Red and White commanders while travelling through Finland during the Civil War; liaising with Admiral Aleksandr Vasiliyevich Kolchak and the White armies in Harbin, China, 1918; liaising with General Mikhail Konstantinovich Dieterichs, Czechoslovak Legions, and a special mission to Ataman Grigory Mikhaylovich Semyonov (or Semenov) in Chita, Transbaikalia, November 1918; activities as General Sir Harry Knox's liaison officer at the White Army Headquarters in Omsk, November 1918 - November 1919; the retreat from Omsk to Vladivostock following the success of the Bolshevik army, November 1919 - March 1920; stationing in Gibraltar and Egypt, 1921-1922; life and work in Simla, Waziristan and Kamptee, India, 1922-1928; work as an intelligence officer, Meshed, Persia (Iran), 1928-1931; life and work in Bombay, Ajmer, Jhansi, Alwar and Delhi, India, 1932-1935, including description of rioting under the Maharajah of Alwar; experiences working in India, China and Egypt during World War Two, including visit to Palestine; account of working in the post-war timber trade and as a consultant in the Russian Section of the London Chamber of Commerce. Also article 'Anglo-Russian Timber Trade: Personal Reminiscences and Reflections of Col L Steveni', The Timber Trades Journal , 11 March 1961, and article by Richard J Aldrich, University of Nottingham, from Modern Asian Studies 32, 1 (1998), pp. 179-217, entitled "Britain's Secret Intelligence Service in Asia during the Second World War" including analysis of Steveni's role as Director of British Secret Intelligence Service (SIS) in Asia.